In turbojets having a centrifugal compressor/diffuser, the diffusion stream of compressed air coming from the diffuser (more precisely from the flow-straightening outlet 15 of the diffuser) shown in fine lines in FIG. 1 is directed more or less perpendicularly to the central portion 32 of the chamber end wall. This orientation depends, amongst other things, on the general inclination of the combustion chamber 24 relative to the axis of rotation 10 of the turbomachine. The chamber 24 can be inclined to a greater or lesser extent so as to reduce its axial size (i.e. length along the axis 10).
With such a diffusion stream, the assembly flanges 34 and 38 form an obstacle to the flow of compressed air, thereby creating turbulence downstream from said flanges. In order to limit such turbulence, it is known to fit an annular fairing piece 33 on the outside face of the flange 38. The free edge 33A, or upstream edge, of said piece 33 is curved towards the central portion 32 of the chamber end wall 30 so as to form a slope encouraging streamlined flow around said flanges 34, 38 and limiting head losses as much as possible.
The structure of the FIG. 1 combustion chamber is nevertheless complex. Furthermore, the annular fairing piece together with the outer wall 28 forms a downward step 35 (see FIG. 1A) that creates turbulence in the flow of air past said step.